Carburetor with combined piston motor and diaphragm motor choke valve actuation

ABSTRACT

Reduction of exhaust emissions is obtained by controlling the carburetor choke valve with greater flexibility. A piston motor responsive to manifold vacuum opens the choke valve partially soon after the engine starts. A diaphragm motor responds to engine vacuum more slowly than the first motor. The diaphragm acts through a modulating spring to open the choke valve, which is connected to a thermostatic coil spring urging the choke valve closed at low ambient temperatures. At high ambient temperatures, actuation of the diaphragm causes wide opening of the choke valve, and at low ambient temperature causes less initial opening, followed by further opening of the choke valve as the engine warms up.

United States Patent 1 1 [11] 3,814,390 Winkley June 4, 1974 CARBURETORWITH COMBINED PISTON 3,321,194 5/1967 Carlson 261/39 B MOTOR ANDDIAPHRAGM MOTOR CHOKE VALVE ACTUATION [75] Inventor: Jerry H. Winkley,St. Louis, Mo.

[73] Assignee: ACF Industries Incorporated, New

York, N.Y.

[22] Filed: July 5, 1972 [2]] Appl. No.: 269,124

[52] US. Cl 261/39 B, 261/39 C [51] Int. Cl. F02m 1/10 [58} Field ofSearch 261/398, 39 C [56] References Cited UNITED STATES PATENTS3,159,692 12/1964 Kittler 261/39 B 3,253,781 5/1966 3,262,683 7/1966Ball et al, 261/39 B 3,272,486 9/1966 Lucas et al 261/39 B 3.321.1935/1967 Highley 261/39 B Primary Examiner-Tim R. Miles Attorney, Agent,or FirmEdward H. Casey 5 7 ABSTRACT Reduction of exhaust emissions isobtained by controlling the carburetor choke valve with greaterflexibility. A piston motor responsive to manifold vacuum opens thechoke valve partially soon after the engine starts. A diaphragm motorresponds to engine vacuum more slowly than the first motor. Thediaphragm acts through a modulating spring to open the choke valve,which is connected to a thermostatic coil spring urging the choke valveclosed at low ambient temperatures. At high ambient temperatures,actuation of the diaphragm causes wide opening of the choke valve, andat low ambient temperature causes less initial opening, followed byfurther opening of the choke valve as the engine warms up.

6 Claims, 4 Drawing Figures PAIENTED B I 3814.390

satin or 2 FIGURE 2.

MTENTEDJUII 4 m4 3814.390 sum 2 or 2 WIVZ/M FIGURE 3.

FIGURE 4.

CARBURETOR WITH COMBINED PISTON MOTOR AND DIAPHRAGM MOTOR CHOKE .VALVEACTUATION BACKGROUND OF THE INVENTION The automatic choke of acarburetor is required to provide an excess of fuel for the engineduring cranking, and a leaner mixture of air and fuel after the enginestarts. As the engine heats up, progressive further opening of the choketo provide further leaning of the airfuel mixture is desirable. Thechoke is usually biased toward its closed position by a thermostaticspring coil, and it has been proposed to connect a vacuum motor actingagainst the thermostat coil to open the choke to meet the operatingrequirements. This is disclosed in U.S. Pat. No. 3,321,193, issued toWenford E. Highley, and U.S. Pat. No. 3,321,194 issued to Harold A.Car]- son, both dated May 23, 1267. Such arrangements, however, are notflexible enough to provide satisfactory adjustments of the choke underthe variety of operating conditions normally encountered. It is,therefore, an object of the invention to refine the control of the chokeso as to reduce engine exhaust emissions during engine starting and warmup.

SUMMARY OF THE INVENTION A carburetor choke is connected to the usualthermostat spring coil which acts to close the choke at lowtemperatures. A vacuum motor has a movable diaphragm, and a linkextending from thediaphragm is urged to a retracted position by amodulator spring. A lever connects the link to the shaft of the choke.One side of the diaphragm is exposed to engine manifold suction througha delay device having a small orifice. The choke shaft also is connectedto a piston in a cylinder having a passageway opening into the mixtureconduit of the carburetor. When the engine starts, the pressure in thecylinder drops and the piston moves down to open the choke slightly.Thus a relatively rich airfuel mixture is provided for the first fewseconds of engine running. The suction applied to the diaphragm buildsup slowly over a period possibly as long as 3 to 45 seconds, due to thedelay device. When the diaphragm moves. only slightly leaner fuel ratiosare provided at cold ambients. since the movement of the diaphragm ispartly absorbed by compression of the modulator spring. But considerablyleaner ratios are provided at warmer ambient temperatures, because athigh temperatures, the spring coil relaxes, and the modulator spring inthe suction motor overrides the spring coil to open the choke valverather widely. The pistonand cylinder motor provides a fail-safefeature, in the event the delay device malfunctions, or becomes blocked,or the diaphragm fails to open the choke sufficiently for the engine tooperate. The diaphragm and modulator spring provide an increasedlean-out effect after an initial running period at warm ambients, orwhen the engine warms up, to permit reduced exhaust emissions.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic view, partly insection, showing the choke valve closed.

FIG. 2 is a partial schematic view showing the choke valve operated toan open position by the piston motor.

FIG. 3 is a view similar to that of FIG. 1 with the diaphragm motoractuated.

FIG. 4 is another schematic view showing the position of the choke valveat high ambient temperatures or after the engine has warmed up, with thediaphragm motor actuated.

DESCRIPTION OF THE PREFERRED EMBODIMENT The invention relates toimproved apparatus for controlling an automatic choke so as to obtainreliable engine starting with reduced exhaust emissions. To achievethese results, a given program of choke opening is required for lowambient temperatures, and a different program of choke opening is neededat higher ambient temperatures above about F. during engine starting andwarm up. The choke valve is opened in stages: first, a minimal openingby a piston motor immediately after engine starting, then delayedfurther opening of the choke by a spring modulated diaphragm motor, andprogressive further opening of the choke valve during engine warm up, ifthe ambient temperature is low.

Referring to the drawing, carburetor 10 has a body 12 enclosing amixture chamber 14 provided with a throttle l6 and chokevalve 18. Thelatter is mounted on shaft 20, which has lever arms 22 and 24.Thermostatic coil spring 26 has one end 27 fixed and its other end 28adapted to abut lever arm 24. Choke valve 18 is of the unbalanced type,normally urged open by the air pressure on its top side as well as bygravity. Air motor 30 includes cylinder 31 and piston 32 fixed to link34, which is looped over the upper edge of lever arm 22. Passage 36connects the bottom of cylinder 31 to mixture chamber 14 below throttle16 in order to expose cylinder 31 to engine manifold vacuum.

Vacuum motor 40 mounted on bracket 41 includes a diaphragm 42 urged tothe right in FIG. 1 by spring 44. Motor 40 is connected by conduit 46 toengine vacuum through a delayer consisting of a plug 48 having a smallorifice 50. Casing 52 has a slidable hub 54 in which link 56 is slidablymounted. The inner end of link 56 has a flange 58 and a modulator spring60 tends to move link 56 inwardly of hub 54 into engagement with abutton 62 at the center of diaphragm 42. Link 56 includes a hollowmember 64 in which rod 66 with flanged end 68 has a limited telescopingmovement,

and the outer end of rod 66 is connected to lever arm 24 of the chokevalve. Link 56 thus provides a lost motion connection between lever arm24 and motor 40 to permit choke valve 18 to be moved finally to a fullyopen position by the action of the air stream and gravity on theunbalanced choke valve.

The operation of the choke valve may be summarized as follows. It isassumed that choke valve 18 is closed, as shown in FIG. 1, and theengine is cranked for starting. As soon as the engine starts, a vacuumis created in mixture chamber 14 and communicated through passage 36 tocylinder 31. Piston 32 then moves downward from the position shown inFIG. 1 to the position shown in FIG. 2, and choke valve 18 is pulledopen by rod 34, acting against the closing force imposed on lever arm 24by thermostatic spring coil 26. Thus a slight opening of the chokevalve. is obtained promptly to prevent a rich or loading" condition fromdeveloping when the engine begins to run. As manifold vacuum is appliedto motor 40, delay device 48, 50 causes diaphragm 42 to move graduallyduring an interval which may be as long as 30 to 45 seconds. Eventuallydiaphragm 42 moves from the position shown in FIG. 2 to the positionshown in H6. 3, and in so doing compresses spring 44, moves button 62away from flange 58 of link 56, compresses modulator spring 60, andopens choke valve 18 further. The further opening of choke valve 18 isopposed and limited by thermostatic coil spring 26 in accordance withthe temperature thereof. Choke valve may then reach a third positionsuch as shown in FIG. 3, if the ambient temperature is low (appreciablybelow 70F, say) and the engine has not yet warmed up, because thenthermostatic srping 26 is stiff enought to overcome modulator spring 60.As the engine warms up, thermostatic'spring 26 relaxes and is overridenby modulator spring 60, which moves link 56 and opens choke valve 18further, as indicated in FIG. 4. The lost motion connection betweenelements 64 and 66 of link 56 permits choke valve 18 to be moved to thefully open vertical position by the air stream.

The mechanism disclosed herein leans out the airfuel mixture promptlyand progressively at low or at high ambient temperatures during enginestarting and warm up to permit favorable engine starting conditions andat the same time maintains the air-fuel ratio at values which reduce thegenerally high emissions during engine starting. Piston motor 30 alsomay serve as a fail-safe device in the event of failure of diaphragmmotor 40, since it independently opens the choke valve sufficiently toallow the engine to run, and the choke valve is then able to openprogressively as the engine warms up and causes the thermostatic coilspring to relax and release the choke valve.

Choke lever arm 22 is loose on shaft 21 and is provided with a tab 23.When lever arm 22 moves in clockwise direction, then tab 23 picks uplever arm 24 which is fast on shaft 20. Thus, movement of lever arm 22by way of tab 23, moves the lever arm 24 causing the partial initialopening of choke 18 as required by the invention. Movement of choke 18by piston 32 is limited by the fact that the piston can traveldownwardly only until it intersects crosspassage 36 which applies vacuumto the piston 32. The length of the piston 32 and the cylinder 31 can beadjusted to give the required amount of movement of piston 32 to satisfythe engine operating conditions. Alternatively, the length of link 34can be adjusted to achieve the same results.

I claim:

l. A carburetor device for an internal combustion engine having a body,a mixture conduit extending through said body, a movable throttle valvein said mixture conduit, a choke valve in said mixture conduit upstreamof said throttle valve and mounted on a shaft for rotation from an opento a closed position, a vacuum motor, means forming a vacuum passageextending from said motor to said mixture conduit at a point belowsaid-throttle valve for providing engine manifold vacuum to said motor,a mechanical connection be tween said vacuum motor and said choke valveto move said choke valve to a partially open position in response toengine vacuum, a temperature responsive spring connected to said chokevalve for biasing it closed at temperatures below a predetermined value,said vacuum motor being capable of overriding said temperatureresponsive spring for partially opening said choke valve when the enginestarts, a second vacuum motor having a movable member and beingresponsive to engine vacuum posterior to said throttle, delay means forretarding the response of said second vacuum motor engine vacuum, a linkconnected to the shaft of the choke valve, and a resilient connectionbetween said movable member of the second vacuum motor and said link,said resilient connection being capable of overriding said temperatureresponsive spring when the latter has a temperature above apredetermined value, whereby the choke valve is opened partially by thefirst vacuum motor when the engine starts running and thereafter isopened further, as the temperature of the temperature responsive springincreases.

2. Apparatus according to claim 1, wherein said movable member of thesecond vacuum motor includes a diaphragm and a spring urging thediaphragm to its inoperative position.

3. Apparatus according to claim 2, wherein said choke valve is anunbalanced valve mounted for free opening by the air stream passingtherethrough.

4. Apparatus according to claim 2, wherein said resilient connection isa spring acting between the diaphragm and link to urge the choke valveopen.

5. Apparatus according to claim 4, wherein said delay means is a memberhaving a restricted orifice in a conduit connecting the second vacuum'motor to a source of engine vacuum.

6. A carburetor devicefor an internal combustion engine having a body, amixture conduit extending through said body,-a movable throttle valve insaid mixture conduit, an unbalanced choke valve in said mixture conduitupstream of said throttle valve, a vacuum piston motor, a passageextending from said motor to said mixture conduit for providing a sourceof engine manifold vacuum to said motor, a mechanical connection betweensaid vacuum motor and said choke valve to move said choke valve to apartially open position in response to engine vacuum, a temperatureresponsive spring connected to said choke valve for biasing it closed attemperatures below a predetermined value, said vacuum motor beingcapable of overriding said temperature responsive spring for partiallyopening said choke valve when the engine starts, a diaphragm vacuummotor responsive to engine vacuum, delay means for retarding the rate atwhich said diaphragm motor responds to the enginevacuum, a linkconnecting the diaphragm of the motor to the shaft of the choke valve,and a resilient connection between the diaphragm and said link, saidresilient connection being capable of overriding said temperatureresponsive spring when the latter has a temperature above apredetermined value, whereby the choke valve is opened partially by thefirst vacuum motor when the engine starts running and thereafter isopened further as the temperature of the temperature responsive springincreases.

1. A carburetor device for an internal combustion engine having a body,a mixture conduit extending through said body, a movable throttle valvein said mixture conduit, a choke valve in said mixture conduit upstreamof said throttle valve and mounted on a shaft for rotation from an opento a closed position, a vacuum motor, means forming a vacuum passageextending from said motor to said mixture conduit at a point below saidthrottle valve for providing engine manifold vacuum to said motor, amechanical connection between said vacuum motor and said choke valve tomove said choke valve to a partially open position in response to enginevacuum, a temperature responsive spring connected to said choke valvefor biasing it closed at temperatures below a predetermined value, saidvacuum motor being capable of overriding said temperature responsivespring for partially opening said choke valve when the engine starts, asecond vacuum motor having a movable member and being responsive toengine vacuum posterior to said throttle, delay means for retarding theresponse of said second vacuum motor engine vacuum, a link connected tothe shaft of the choke valve, and a resilient connection between saidmovable member of the second vacuum motor and said link, said resilientconnection being capable of overriding said temperature responsivespring when the latter has a temperature above a predetermined value,whereby the choke valve is opened partially by the first vacuum motorwhen the engine starts running and thereafter is opened further as thetemperature of the temperature responsive spring increases.
 2. Apparatusaccording to claim 1, wherein said movable member of the second vacuummotor includes a diaphragm and a spring urging the diaphragm to itsinoperative position.
 3. Apparatus according to claim 2, wherein saidchoke valve is an unbalanced valve mounted for free opening by the airstream passing therethrough.
 4. Apparatus according to claim 2, whereinsaid resilient connection is a spring acting between the diaphragm andlink to urge the choke valve open.
 5. Apparatus according to claim 4,wherein said delay means is a member having a restricted orifice in aconduit connecting the second vacuum motor to a source of engine vacuum.6. A carburetor device for an internal combustion engine having a body,a mixture conduit extending through said body, a movable throttle valvein said mixture conduit, an unbalanced choke valve in said mixtureconduit upstream of said throttle valve, a vacuum piston motor, apassage extending from said motor to said mixture conduit for providinga source of engine manifold vacuum to said motor, a mechanicalconnection between said vacuum motor and said choke valve to move saidchoke valve to a partially open position in response to engine vacuum, atemperature responsive spring connected to said choke valve for biasingit closed at temperatures below a predetermined value, said vacuum motorbeing capable of overriding said temperature responsive spring forpartially opening said choke valve when the engine starts, a diaphragmvacuum motor responsive to engine vacuum, delay means for retarding therate at which said diaphragm motor responds to the engine vacuum, a linkconnecting the diaphragm of the motor to the shaft of the choke valve,and a resilient connection between the diaphragm and said link, saidresilient connection being capable of overriding said temperatureresponsive spring when the latter has a temperature above apredetermined value, whereby the choke valve is opened partially by thefirst vacuum motor when the engine starts running and thereafter isopened further as the temperature of the temperature responsive springincreases.